Summary of Information with Regard to Outstanding Warrants Issued in Connection with Equity and Debt Financing and Consultants (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 30, 2010
Equity [Line Items]
Number Issued	12,538,204
Exercise Price		$ 7.20
February 12, 2009 Series B-1 Transaction
Equity [Line Items]
Exercisable Date	February 12, 2009
Number Issued	1,200,000
Exercise Price	$ 3.00
Expiration Date	Feb. 12, 2024
May 13, 2009 Series B-2 Transaction
Equity [Line Items]
Exercisable Date	May 13, 2009
Number Issued	600,000
Exercise Price	$ 3.00
Expiration Date	May 13, 2024
June 30, 2009 Series B-2 Transaction
Equity [Line Items]
Exercisable Date	June 30, 2009
Number Issued	333,333
Exercise Price	$ 3.00
Expiration Date	Jun. 30, 2024
August 12, 2009 Series B-2 Transaction
Equity [Line Items]
Exercisable Date	August 12, 2009
Number Issued	200,000
Exercise Price	$ 3.00
Expiration Date	Aug. 12, 2024
September 30, 2009 Series B-2 Transaction
Equity [Line Items]
Exercisable Date	September 30, 2009
Number Issued	216,666
Exercise Price	$ 3.00
Expiration Date	Sep. 30, 2024
November 4, 2009 Series B-2 Transaction
Equity [Line Items]
Exercisable Date	November 4, 2009
Number Issued	106,666
Exercise Price	$ 3.00
Expiration Date	Nov. 04, 2024
December 8, 2009 Series B-2 Transaction
Equity [Line Items]
Exercisable Date	December 8, 2009
Number Issued	133,143
Exercise Price	$ 3.00
Expiration Date	Dec. 08, 2024
January 29, 2010 Series B-2 Transaction
Equity [Line Items]
Number Issued	216,667
Exercise Price	$ 3.00
Exercisable Date	Jan. 29, 2010
Expiration Date	Jan. 29, 2025
March 8, 2010 Series B-2 Transaction
Equity [Line Items]
Number Issued	223,334
Exercise Price	$ 3.00
Exercisable Date	Mar. 08, 2010
Expiration Date	Mar. 08, 2025
April 30, 2010 Series B-2 Transaction
Equity [Line Items]
Number Issued	204,192
Exercise Price	$ 3.00
Exercisable Date	Apr. 30, 2010
Expiration Date	Apr. 30, 2025
May 10, 2010 Series B-2 Transaction
Equity [Line Items]
Number Issued	143,166
Exercise Price	$ 3.00
Exercisable Date	May 10, 2010
Expiration Date	May 10, 2025
November 25, 2015 Offering Warrants
Equity [Line Items]
Number Issued	1,180,240
Exercise Price	$ 2.50
Exercisable Date	May 25, 2016
Expiration Date	May 25, 2021
September 22, 2016 Series B-3 Transaction
Equity [Line Items]
Expiration Date	September 22, 2023
Number Issued	698,158
Exercise Price	$ 3.00
Exercisable Date	Sep. 22, 2016
September 29, 2016 Series B-3 Transaction
Equity [Line Items]
Number Issued	846,100
Exercise Price	$ 3.00
Exercisable Date	Sep. 29, 2016
Expiration Date	Sep. 29, 2023
December 22, 2016 Private Placement Warrants
Equity [Line Items]
Number Issued	1,466,204
Exercise Price	$ 5.00
Exercisable Date	Dec. 22, 2016
Expiration Date	Dec. 23, 2023
December 23, 2016 Series B-3 Transaction
Equity [Line Items]
Number Issued	924,780
Exercise Price	$ 3.00
Exercisable Date	Dec. 23, 2016
Expiration Date	Dec. 23, 2023
December 28, 2016 Private Placement Warrants
Equity [Line Items]
Expiration Date	December 28, 2023
Number Issued	644,468
Exercise Price	$ 5.00
Exercisable Date	Dec. 28, 2016
February 27, 2017 Private Placement Warrants
Equity [Line Items]
Number Issued	76,776
Exercise Price	$ 5.00
Exercisable Date	Feb. 27, 2017
Expiration Date	Feb. 27, 2024
2018 and 2017 Warrants issued for services
Equity [Line Items]
Exercisable Date	Various dates in 2018<br/>and 2017
Expiration Date	Various dates in 2025<br/>and 2024
Number Issued	2,157
Exercise Price	$ 5.00
December 19, 2017 Line of Credit Warrants
Equity [Line Items]
Number Issued	500,000
Exercise Price	$ 5.00
Exercisable Date	Dec. 19, 2017
Expiration Date	Dec. 19, 2024
May 23, 2019 Rights offering warrants
Equity [Line Items]
Number Issued	2,622,154
Exercise Price	$ 7.00
Exercisable Date	May 23, 2019
Expiration Date	May 23, 2026